Patent GB-263530-A (GB)
Title: Improvements in methods of signalling on board ships
IPC: B63B45/08
Filed: 1925-09-28
Abstract: 263,530. Henderson, Sir J. B. Sept. 28, 1925. Bearings, indicating; mariners' compasses.- Apparatus enabling an observer on a convoyed or other ship to determine the difference between the readings of his compass and of the compass on the leader of the convoy or other ship comprises an apparatus on the leader for automatically transmitting signals indicating azimuth bearings according to its compass, and a sighting device on the observer's ship enabling the observer to obtain the reading on his compass of a bearing signalled by the leader; the signal transmitting device may be stationed on shore and be used without a compass. Fig. 1 shows a transmitter having a compass card 7 controlled by the master gyro-compass on the leader, the card being secured to a spur wheel 12 driven by a step-by-step motor 6. The wheel 12 carries a motor 14 which continuously rotates, through gearing 15 - - 20, a vertical shaft 13 carrying a multiple collimator 21. As shown, the collimator comprises sixty objectives 23, exactly 6‹ apart, a tube 25 having sixty vertical slits 26 cut in it, and a central lamp 24. A " zero lamp " 22 is provided above the collimators, and its lighting circuit is momentarily made or broken each time one of the lines of collimation, during its rotation, passes over the zero reading of the compass card 7. The making or breaking of the lamp circuit is effected by the engagement of an insulated pin 32 on a wheel 17 with contacts 33 in the circuit. An observer, knowing the rate of rotation of the collimators, and the azimuth reading, to the nearest multiple of 6‹, of the line of sight between him and the transmitter, can determine the azimuth reading as shown on the card 7, if he measures the time between one flash of the lamp 22 and his reception of a collimated beam. Fig. 4 shows a receiver, for use by the observer, comprising a compass card 44 driven from the master compass, and a sighting telescope. The objective 74 and eye piece 75 of the telescope are carried by a rotatable upper part 38 of the instrument casing, and a prism system 52 forming part of its optical system is carried by a fork 51 rigidly attached to a spider 49 rotatable round the axis of the card. The spider is normally stabilized by the card, but may be turned relatively thereto by a knob 66 on a spindle 65 carrying a pinion 67 engaging a pinion 58 on a spindle 55 carried by the spider, a second pinion 57 on the spindle 55 being in engagement with a toothed wheel 71 fixed to the card. The spindle 55 carries, also, a scale drum 60, graduated in minutes and covering 10‹, and a bevel gear 59 which is in driving engagement with a rotating graduated dial 61 indicating 6‹ per revolution. A pointer 72, against which both the scale 70 of the card 44 and the scale 60 are read, and a pointer 61a, against which the dial 61 is read, are carried by the spider, and the arrangement is such that the reading on the dial 61 is equal to the reading on the scales 70, 60 less multiples of 6‹. The receiver may be operated to read azimuth by first turning the casing 38 into the approximate direction of sight, and then rotating the knob 66, thus turning the prisms and scales, to sight accurately. To render calculation unnecessary when comparing compass readings the receiver is provided with a pointer 63 which is turned over the dial 61 when required by a motor 50 also carried by the spider. The motor 50 drives the friction bevel 69 which may be operatively connected to a friction bevel 64 on the spindle 62 of the pointer 63 by raising the knob 66, the spindle 65 of which loosely carries a friction bevel 68 to engage the bevels 69, 64. The observer, when comparing compass readings, first raises the knob 66 until the pointer 63 is brought opposite the fixed pointer 61<a> He then turns the knob to sight on the lamp 22. When the lamp 22 flashes, he again raises the knob to cause the pointer 63 to rotate, and continues to train the sight until a collimator flash is seen; he 'then stops training and lowers the knob. The reading of the pointer 63 on the dial 61 then shows the difference between the readings of the two compass cards. Means for elevating and depressing the prisms 52, to cope with the rolling of the ship, is provided consisting of a stem 80 secured to the prisms and engaging a forked arm 78 rotatable about a horizontal axis bv an external knob. The collimator system may be replaced by a collimator on the receiver, either in place of the knob for elevating the prisms or mounted on the prism carrier, and by sixty double reflectors on a horizontal wheel in place of the multiple collimator 21. A modification of the transmitter is described in which the collimator beams are 12‹ apart, and four clock faces each having two hands, making respectively one and twelve revolutions during movement of the collimator beams through 12‹, are provided, the lamp 22 being omitted. The pointer 63, motor 50, &c., may then be omitted from the receiver, and the azimuth reading on the compass of the transmitter may be determined by simultaneous observation of the collimator flash and a clock face. If the transmitter is to be capable of use only when there is a rate of change of bearing between the ships, the collimators or reflectors may be fixed to the card of the transmitter so that each corresponds with a 6‹ mark, and the driving gear and the lamp 22 may be omitted. If the transmitter is mounted on shore, it may comprise one or more collimators or reflectors which may be rotatable, or may be fixed and arranged at known angles to the meridian, the compass being omitted. The Provisional Specification describes a transmitter comprising one collimator and a pointer rotating over the compass card, and a receiver having two pointers rotating over its compass card.